Stabilization of lubricants



2,910,437 STABILIZATION F LUBRICANTS Ted Symon, Hinsdale, Ill., assignor, byxmesne assignmentsyto Universal Oil Products Company, Des -Pla1nes, Ill.,.a corporation-of Delaware 'No'DraWing; Application March 9, 1956 Serial No. 570,420 4 Claims. 3 01. 252-32 "The invention isparticularly applicable to the stabilizati'on of greases, either of synthetic orpetroleum origin.

The synthetic greases generally'are referred to as lithium base grease, sodium base-grease, calcium base grease, barium base-grease, strontium base 'grease, aluminum base grease, etc. These greases are solid or semi-solid gels and, in generaL-are prepared by the addition to mineral or synthetic oils of hydrocarbon-soluble metal soaps or salts of higher fatty acids as, for example, lithium stearate, calcium stearate, aluminum naphthenate, etc. The grease may contain thickening agents such as silica, carbon black, polyacrylatesftalc, etc. Another type of grease is prepared from oxidized petroleum wax, to which the saponifiable base is combined with the proper amount of the desired sapom'fying agent, and the resultant mixture processed to produce a grease. Other types of greases in which the features of the present invention are usable include petroleum grease, whale grease, wool grease, etc., and those made from inedible fats, tallow, butchers waste, etc.

The present invention also is particularly applicable to the stabilization of lubricating oils, including those of petroleum or synthetic origin. The synthetic lubricants are of varied types including aliphatic esters, polyalkylene oxides, silicones, esters of phosphoric and silicic acids,

highly fluorine-substituted hydrocarbons, etc. Of the aliphatic esters, di-(Z-ethylhexyl) sebacate is being used on a comparatively large commercial scale. Other aliphatic esters include dialkyl azelates, dialkyl suberates,

2,910,437. e r Patented Oct. 2'7, 1959 ICC or lower concentrations may be employed. The exact concentration to be used will depend upon the particular organic substance being treated. a In most cases concentrations of from about 0.01% to about 3% by weight generally will be employed.

Itis understood that the inhibitor may be used along with other additives incorporated in the organic substance. For example, in grease the inhibitor may be used along with higher alcohols, esters, organic amines, poly butene, suI-furized fatty materials, sulfur chlorine compounds, 'dyes, perfumed materials, fillers, etc. In some 7 cases, it may be of advantage to also include a metal include methyl silicone, methylphenyl silicone, etc., and

the silicates include, for example, tetraisooctyl silicate, etc. The highly fiuorinated hydrocarbons include fluo rinated oil, perfiuorohydrocarbons, etc.

In a specific embodiment the present invention relates to a method of stabilizing synthetic grease which comprises incorporating therein from about 0.1 to about 5% by weight of 2,4'-,diaminod.iphenyl ether.

In another embodiment the present invention relates to a method of stabilizing lubricating oil against oxida tive deterioration which comprises incorporating therein a stabilizing concentration of a 2,4'-diaminodiphenyl ether.

In one embodiment the present invention comprises a 2,4-diaminodipheny l ether. A preferred inhibitor is 2,4-diaminodiphenyl ether. 7

In general, the inhibitor will be utilized in a concentration of from about 0.0001% to about 5% by weight of the organic substance, although in some cases higher trial-kyl deactivator as, for example, disalicylal diamino propane, ethylene diamine tetra-acetic acid tetrasodium salt, etc., or to include other additives such as tricresyl phosphate,

fphenols including 2,6di-tert-butyl-4-rnethylphenol, '2,-4-di-methyl-6-tert-butylphenol, alkylated diphenyl amines, phenyl naphthyl amines, dialkyl phen ylene diamines, phenothiazine, organic selenium compounds, etc., aswell as corrosion inhibitors, extreme pressure additives, viscosity index improvers, etc. When desired, the inhibitor of the present invention may be prepared as amixture with one or more of these other additives and incorporated in this manner in the organic substance or components thereof.

The inhibitor of the present invention may be incorporatedin the organic substance in any suitable manner and at any suitable stage of preparation. For example, in an organic substance which comprises a mixture of several components, as for example, grease, the inhibitor may be added to one or more of the components of the grease prior to compositing and processing thereof or it may be added to the mix at any time, preferably before final processing in order to obtain intimate mixing and dissolving of the inhibitor in the grease.

The following examples are introduced to illustrate further the novelty and utility of the present invention but not with the intention of unduly limiting the same.

Example I 2,4'-diaminodiphenyl ether was utilized as an inhibitor in a lithium grease. The grease was prepared by mixing 91% of a Pennsylvania bright stock with 8% of lithium stearate. The mixture was heated at about 450 F. while agitating the same. Subsequently, the grease was cooled while agitating to 320 F. and, at this'temperature, 1% of 2,4'-diaminodiphenyl ether was added. Agitationwas continued and the mixture was allowed to cool to about 250 F. and the grease then further cooled slowly to room temperature.

The stability of the grease was tested according to a modified Norma Hoffman method, 'in which a sample of I the grease is placed in a bomb in the presence of brass discs acting as an oxidation catalyst and oxygen is charged thereto. The bomb then is heated to 212 F., and the time required for a drop of 5 pounds pressure is taken as the induction period. In this run, a control sample of the grease (not containing this additive) had an induction period of 10.5 hours. On the other hand, a sample of the grease containing 1% by weight of 2,4- diaminodiphenyl ether had an induction period of 260 hours. Thus, it will be noted that the inhibitor of the present invention was exceptionally eliective in improving the stability of the grease.

Example 11 This grease had a control (not containing this additive).

induction period of 10.5 hours. On the other hand,

a sample of this grease containing 1 by weight a" 2,4,'-diaminodiphenyl ether had an induction period of 370 hours. Here again, it will be noted that the inhibitor Example Ill The grease used in this example was a syntheticgrease prepared in substantially the same manner described in Example I, except that 87% of di-Z-ethylhexyl sebacate was mixed with 12% lithium stearate. 1% by weight of 2,4- diaminodiphenyl ether was incorporated in the syn thetic grease. A control sample of the grease (not containing this additive) had an induction period of 17 hours. On the other hand, a sample of the grease containing 1% by weight of 2,4-diamino-dipheny1 ether did not undergo a pressure drop of one pound per square inch until after 318 hours exposure.

From the above data, it will be noted that this inhibitor was very efiective in improving the stability of thesynthetic grease.

I claim as my invention: a p

1. A method of stabilizing a lubricant normally subject to oxidative deterioration which comprises incorporating 25 therein a stabilizing concentration otza' diniiaadiphen r ether.

References Cited in the file of this patent UNITED STATES PATENTS 2,048,362 Stoesser et al. July 21, 1936 2,269,265 Hamilton et al. Jan. 6, 1942 2,290,860 Burk et al. July 28, 1942 2,350,746 Fuller June 6, 1944 2,367,264 Burk et a1. Jan. 16, 1945 2,440,530- Yates Apr. 27, 1948 2,523,100

Eby Sept. 19, 1950 

2. A LUBRICANT NORMALLY SUBJECT TO OXIDATIVE DETERIORATION CONTAINING, AS AN INHIBITOR AGAINST SAID DETERIORATION, A STABILIZING CONCENTRATION OF 2,4''-DIAMINODIPHENYL ETHER. 